arbon, as with many elements, can arrange its atoms into several different geometries, or "allotropes." In pure diamond, every carbon atom is covalently bonded to exactly 4 other carbon atoms in a very specific and energetically favorable geometry. The diamond cannot be broken or scratched unless many covalent bonds are broken, which is difficult to do. In another common allotrope, graphite, every carbon atom is covalently bonded to only 3 other carbon atoms, and the atoms are arranged in sheets that are not covalently bonded to each other. The sheets can be broken apart easily, ultimately meaning that graphite can be easily scratched. Coal is composed of particles of different allotropes of carbon, and some "amorphous carbon," which has no defined geometry in its atomic structure. Without a continuous network of covalent bonds, coal is easily scratched (i.e. it is not hard).
Answer:
Hydrogen atom of one molecule and carbon atom SPF another molecule
Answer:
What best describes how transferrin is transported through the erythrocyte plasma membrane is receptor-mediated endocytosis.
Explanation:
The incorporation of transferrin across the erythrocyte membrane depends on a transferrin receptor expressed on the surface of the membrane. The specific receptor recognizes the presence of iron-charged transferrin, transferin diferrica, incorporating it into the cell by endocytosis. Once in the cytoplasm, the iron is dissociated from the transferrin.
Free transferrin is called apotransferrin. The transferrin receptor has a high affinity for transferrin di-ferrica, which facilitates its incorporation by endocytosis, and the release of apotransferrin into the extracellular space.
The other options are not correct because:
<em> A. </em><u><em>Exocytosis</em></u><em> implies the exit of substances from the cell.</em>
<em> B. </em><u><em>Pinocytosis</em></u><em> involves the invagination of the membrane to incorporate soluble substances into the cell.</em>
<em> C. </em><u><em>Phagocytosis</em></u><em> is the incorporation of solid substances by invagination of the membrane.</em>
